I've installed the latest version of Foobar2000 v.1.22. I wish to install Kernel Streaming as being a so-called Component. Downloaded the zip-file. Unpacked it. Got .dll file. Put .dll file in the map 'components' + general map of Foobar2000, which is within 'Program Files'.

The Kernel Streaming component is indeed within the overview of the components, but trying to install it remains grey and so I cannot install it.

Downloaded the zip-file. Unpacked it. Got .dll file. Put .dll file in the map 'components' + general map of Foobar2000, which is within 'Program Files'.

This is wrong. Just leave the zip file as it is, and install it using the Install button in the Components dialog of the Preferences; click that, locate the zip folder, and let foobar2000 do it properly. This is explained in the official list of frequently asked questions.

Besides, the Install button is only for components that aren’t already installed. It’s possible that fb2k detected your placed DLL and added it properly already. Did you check the Outputs section of the Preferences to see whether or not you can use Kernel Streaming?